1. Field of the Invention:
This invention relates to an information signal reproducing apparatus and more particularly to an apparatus for reproducing an information signal from a recording medium on which a plurality of different kinds of pilot signals are recorded in a superimposed state on the information signal in predetermined rotation and recording tracks are formed at one of different track pitches.
2. Description of the Related Art:
Some of the rotary head type magnetic recording and reproducing apparatuses of the kind using a magnetic tape (hereinafter referred to as VTR) are arranged to permit selection of different tape travel speeds for recording and reproduction. In other words, they are arranged to be capable of setting different track pitches. The tape travel speed is arranged to be manually changed from one speed over to another by the operator in carrying out recording and to be automatically changed over to an appropriate speed at the time of reproduction by reproducing and using a control signal which is recorded along an edge part of the tape at intervals according to the track pitch employed. The control signal is obtained by frequency dividing a vertical synchronizing signal included in a video signal and is recorded at the edge part of the tape to be reproduced during reproduction. If the control signal is reproduced in a mode differing from a mode employed in recording, the frequency of the reproduced control signal becomes a different frequency. Therefore, during reproduction, the recording tape travel speed is discriminated by measuring the period of the reproduced control signal to find such difference in frequency.
The control signal is provided principally for the purpose of controlling a rotary head or a drive system in such a way as to have the head accurately positioned at an applicable track during reproduction.
Meanwhile, a tracking control method of a higher grade has recently appeared using pilot signals according to the so-called four frequency pilot method. The information signal recording and reproducing apparatus employing the four frequency pilot method does not have the above stated reproduced control signal. Therefore, the above stated tape speed discriminating method is not applicable to the apparatus of that type in case that the apparatus is required to have different tape speeds.
In view of this, a method for detecting a tape travel speed employed in recording has been proposed for the VTR of the type not recording the control signal. For example, U.S. Pat. No. 4,550,345 discloses a VTR which is arranged: To have a standard mode (hereinafter referred to as SP mode) and a long time mode (hereinafter referred to as LP mode) in which the tape travel speed in recording is slower than the speed of the SP mode; and to change the recording rotation of the four different pilot signals according to the SP mode or the LP mode. In other words, with the recording sequence or rotation in which these pilot signals are recorded changed from one rotation over to another, the reproducing tape travel speed is determined by detecting the mode employed in recording through a difference in the sequence of reproduced pilot signals resulting from the change-over of the recording rotation.
In accordance with the above stated arrangement, however, the rotation of the pilot signals must be changed from one rotation over to another according to a change in the recording tape speed. In cases where a VTR is desired to have more than three recording modes, however, it becomes difficult to set the recording rotation of the pilot signals and, for reproduction, a complex circuit must be used in discriminating the mode employed in recording. Besides, in the event of a recording medium (or tape) having pilot signals recorded along with an information signal in specific given sequence of rotation irrespectively of the recording mode (recording track pitch), it is impossible to discriminate the pitch at which the tracks are formed thereon.